This probiotic is fine, perfectly effective if you want a stabilized powder of acidophilus alone. Source Naturals is a high quality brand. Ideally lactobacilis is the dominant bacterium in the small intestine while bifidus bacterium are dominant in the large intestine or bowel. It's best to take both, and other species as well.
I prefer the Life Flora capsules because they contain a combination of probiotics rather than just one, and I find capsules more convenient to take than powder - also it is very pure so there're no substances in it that I react to.
Jarrow EPS capsules and Culturelle capsules are also very good (but the EPS aren't any good if you have dairy and soy intolerances). Sometimes it's worth taking a more expensive probiotic such as culturelle short term and then going back to something you find affordable for most of the time.
I choose stabilised probiotics because I've found them more convenient and just as effective as the refrigerated ones.

I was disappointed with this product because they give you such a small amount for the price. When I opened the bottle it was a bit less than half full. The product itself works well and seems quality, but for the price, they could give you four ounces! I won't reorder this because I can get more probiotics for the same price.